Through the use of specific antisera we will study 1) the surface antigens found on cloned lines of cells from rat and mouse brain, and 2) the expression of these same antigens in normal nervous tissue. These investigations will be aimed specifically at correlating cell surface markers with cell type and at mapping specific cell populations during the development of the mammalian nervous system. The cloned cell lines used in these studies have been identified as neuronal or glial on the basis of electrophysiology and a series of ion flux assays which can detect receptors for neurotransmitters and voltage-dependent Na ion, K ion, and Ca ions. To date, six antigens (N1-N6) have been identified which are specific for cell lines classified as neuronal, two antigens (G1 and G2) have been shown to be specific for glial cell lines, and two others (NG1 and NG2) are present on cell lines with mixtures of neuronal and glial properties. Using immunofluorescence we are studying the cellular distribution of these markers in primary cultures and in frozen sections of rat brain. These studies should show not only which cell types express the various antigens but also how antigen expression changes as a function of development.